A Model for Thermophysical Properties of CO2-Brine Mixtures at Elevated Temperatures and Pressures

Abstract

A mutual CO2-H2O solubility model was previously reported for application to CO2-enhanced geothermal systems. The ability of this model to predict PVT and caloric properties of the compressed gas phase is investigated. Compressibility factors of pure CO2 and CO2-H2O mixtures can generally be predicted within a few percent of reference and experimental data. Caloric data are also reasonably well reproduced for CO2-H2O gas mixtures at moderate water content. At elevated water contents, more significant deviations are observed between model results and published experimental enthalpies of mixing. However, total enthalpies may still be predicted with reasonable accuracy for applications to CO2-enhanced geothermal systems. Experimental data in the temperature and pressure range of most interest to CO2-enhanced geothermal systems are scarce and would be needed for further model validation.